The invention relates to a network coupler for network users in a network comprising at least two lines.
Network couplers are generally used for coupling in and coupling out data transferred via a network. They thus establish the connection between a network user and the network. Data supplied by a network user are coupled into the network by means of the network coupler. Conversely, data transferred through the network are coupled out by means of the network coupler and made available to the network user.
Known network couplers are limited to coupling in and coupling out data.
It is an object of the invention to provide a network coupler which is not only suitable for data transfer but also for energy transfer.
According to the invention, this object is achieved in that the network coupler is formed in such a way that it is suitable for data transfer via the two lines of the network and for coupling out energy from the two lines of the network to which a terminal of a voltage source is coupled, in that the network coupler symmetrically couples energy into and/or out of the two lines, in that the network coupler couples the data symmetrically, differentially and inductively or capacitively into and/or out of the two lines, and in that the network coupler symmetrically terminates the two lines.
For the purpose of data transfer, the data are transferred symmetrically and differentially on the two lines of the network. For example, a data bit transferred through the network lines is, however, transferred with opposite polarities through the two lines. The network coupler couples in or couples out these data inductively or capacitively, as well as symmetrically and differentially.
Moreover, the network coupler is also suitable for energy transfer. A terminal of a voltage source is coupled to the two lines of the network. The network coupler is formed in such a way that it can couple out this energy from the two lines. This is effected symmetrically, i.e. the current drawn by the network coupler from the lines of the network is equally large in the two lines. This is achieved in that the load represented by the network coupler with respect to the two lines of the network is equally large on the two lines, so that the two lines are symmetrically terminated.
It is thereby achieved, on the one hand, that both data and energy transfer is made possible via the network coupler, or via the two lines of the network. Due to the strictly symmetrical coupling-out of supply currents on the two lines and the symmetrical differential transfer of data on the two lines, it is achieved that the data transfer is not disturbed by disturbances on the two network lines, which disturbances may have been caused, for example, by the energy distribution.
Such network couplers can be constructed in a relatively simple and, hence, low-cost way.
An embodiment of the network coupler according to the invention, is characterized by such a simple structure but can nevertheless fulfill the above-mentioned conditions, in which the network coupler comprises a first primary coil having a first terminal which is coupled to the first line of the network, and a second primary coil having a first terminal which is coupled to the second line of the network, and in which the two second terminals of the first primary coil and the second primary coil are interconnected at a power supply point which supplies a power supply voltage, and in which the network coupler comprises a secondary coil by means of which data can be coupled into or out of the two lines of the network, and in which the two primary coils and the secondary coil of a core are magnetically coupled together. The two first and second primary coils which have the same resistance or impedance are used, on the one hand, for coupling out energy from the two lines of the network. This is effected symmetrically, i.e. currents which flow in response to the coupling-out of energy are divided into equal currents on the two lines.
The first primary coil and the second primary coil are magnetically coupled to a secondary coil. In the secondary coil, a voltage is only induced when a differential current flows between the two first terminals of the first and the second primary coil. On the other hand, currents of the same sign in the two windings do not lead to a voltage induction in the secondary coil. It is thereby achieved that data differentially transferred through the two lines lead to a voltage induction in the secondary coil but are not accompanied by disturbances taking place at the same sign, which disturbances may occur, for example, due to fluctuations of the power supply voltage as a result of a varying load.
To achieve the symmetrical coupling-out as described above, the two primary coils are advantageously formed in such a way that a current flowing through the power supply point is divided into two equally large currents flowing in the two lines of the network. In the simplest case, this can be achieved by manufacturing the windings of the same material and giving them the same cross-section, length and the same number of turns.
The ratio of turns between the number of turns of the primary coils and the number of turns of the secondary coil defines the voltage ratio of the differential voltage at the terminals of the secondary coil. It has been proved to be advantageous, as in a further embodiment of the invention that the secondary coil has a higher number of turns than the primary coils.
The primary coils may be constructed in a relatively simple manner in that they are formed, for example, in further embodiments of the invention, as metal strips and may have a number of turns of n=1.
A further advantageous construction of the coils is that they are provided as a printed circuit on a two-layer plate on which both the two primary coils and the secondary coils are printed as conductor tracks.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.